JP2023009792A - Drive device for electric motor - Google Patents

Abstract

To provide a drive device for an electric motor capable of reducing electromagnetic wave noise caused by a filter circuit.SOLUTION: A drive device for an electric motor comprises a filter circuit including a first coil LA and a second coil LB which is disposed in parallel with the first coil LA. The first coil LA and the second coil LB generate magnetic fields in mutually inverse directions. Since the magnetic fluxes of the coils LA and LB are cancelled with each other, by disposing a rotation detection element for detecting a rotation position of the electric motor at an equal distance from the first coil LA and the second coil LB, electromagnetic wave noise that the rotation detection element receives can be reduced as further as possible.SELECTED DRAWING: Figure 6

Description

The present invention relates to an electric motor drive device.

The electric power steering apparatus of Patent Document 1 has two sets of control units for driving electric motors having two sets of independent windings, and supplies power through a single power connector. The connected conductive member is branched into at least two near the power connector, and two sets of power relays, filters, and inverter circuits are arranged symmetrically with respect to the power connector.

WO2018/070004

For example, in a drive device for driving an electric motor having a first winding set and a second winding set, a first drive system for controlling energization of the first winding set and the second winding set In the drive device having the second drive system for controlling the energization of the drive device, the number of elements increases due to redundancy, but there is a demand for downsizing of the drive device.
As a result, the mounting density of the elements on the substrate increases, and there are concerns about malfunctions and deterioration of control accuracy due to interference between the elements.
In particular, the coils that make up the filter circuit generate electromagnetic noise, which may adversely affect elements such as a motor rotation position sensor that are arranged around.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electric motor driving device capable of reducing electromagnetic noise caused by a filter circuit.

In one aspect, an electric motor drive device according to the present invention has a filter circuit including a first coil and a second coil arranged in parallel with the first coil, The second coils generate magnetic fields in mutually opposite directions.

According to the present invention, electromagnetic noise due to the filter circuit can be reduced.

1 is a configuration diagram of an electric power steering device; FIG. It is a block diagram of a drive. It is an exploded perspective view of a motor unit. It is a circuit diagram of a filter circuit. 2 is a layout diagram of coils and capacitors that constitute a filter circuit; FIG. FIG. 4 is a state diagram showing the magnetic field generated by the coil; It is a circuit diagram of a filter circuit. 2 is a layout diagram of coils and capacitors that constitute a filter circuit; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an electric motor drive device according to the present invention will be described below with reference to the drawings.
An embodiment in which the electric motor driving device according to the present invention is applied to an electric power steering device for a vehicle will be described below, but the electric motor driving device according to the present invention can be applied to devices other than the electric power steering device. is clear.

FIG. 1 is a configuration diagram showing one aspect of an electric power steering device.
The electric power steering device 200 includes a steering mechanism 210 that steers the front wheels 110 , 110 that are steered wheels of the vehicle 100 , and a motor unit 220 that imparts a steering force to the steering mechanism 210 .
The electric power steering apparatus 200 applies the steering force by the motor unit 220 to assist the driver's steering force or for autonomous steering.

The motor unit 220 integrally includes an electric motor 230 and a driving device 240 that drives the electric motor 230 .
The electric motor 230 is a brushless DC motor and has two sets of windings, ie, a first winding set and a second winding set, each composed of a U-phase coil, a V-phase coil, and a W-phase coil.
The drive device 240 includes a first drive system that controls energization of the first winding set of the electric motor 230 and a second drive system that controls energization of the second winding set of the electric motor 230. .

Here, the first drive system and the second drive system are respectively configured by the same components, the first drive system can independently supply power to the first winding set, and the second drive system can independently power the second set of windings.
In other words, the drive device 240 has a redundant first drive system and a second drive system.

The steering mechanism 210 includes a steering wheel 201 , a steering shaft 202 , a pinion shaft 203 and a rack shaft 204 .
The reduction mechanism 205 transmits torque generated by the electric motor 230 to the rack shaft 204 .
When the driver of vehicle 100 rotates steering wheel 201 , steering mechanism 210 transmits steering torque to pinion shaft 203 via steering shaft 202 .
The steering mechanism 210 converts the rotational motion of the pinion shaft 203 into linear motion of the rack shaft 204 to steer the front wheels 110 , 110 connected to both ends of the rack shaft 204 .

A steering torque sensor 206 detects the steering torque of the steering wheel 201 .
Vehicle speed sensor 207 detects the running speed of vehicle 100 .
When performing steering assistance, drive device 240 sets a control target value (for example, , torque command value).
Then, the drive device 240 performs PWM (Pulse Width Modulation) control of energization to each winding set of the electric motor 230 based on the calculated control target value.

FIG. 2 is a block diagram showing the configuration of the driving device 240. As shown in FIG.
The driving device 240 controls the energization of the first winding set 230B of the electric motor 230 and the first control unit 240A that constitutes a first drive system that controls the energization of the first winding set 230A of the electric motor 230. and a second control unit 240B forming a second drive system.

The first control unit 240A includes a control circuit section 241A, a power relay 242A, a filter circuit 243A (first filter circuit), an inverter circuit 244A, and the like.
The control circuit section 241A includes an MPU (microprocessor unit) 241A1, an input circuit 241A2, a drive circuit 241A3, and the like.

The second control unit 240B includes a control circuit section 241B, a power relay 242B, a filter circuit 243B (second filter circuit), an inverter circuit 244B, and the like.
The control circuit unit 241B includes an MPU 241B1, an input circuit 241B2, a drive circuit 241B3, and the like.
The MPUs 241A1 and 241B1 can also be called processors, CPUs (Central Processing Units), processors, arithmetic units, or microcomputers.

The power relays 242A, 242B operate in accordance with command signals from the control circuit units 241A, 241A to turn on and off circuits that supply power from a battery (not shown), which is the power source of the electric power steering device 200, to the inverters 244A, 244B. do.
The filter circuits 243A, 243B are provided on power lines between the power relays 242A, 242B and the inverters 244A, 244B.

The filter circuits 243A and 243B are LC filters in which a coil L (inductor) is connected in series with the signal source and a capacitor C is connected in parallel with the load.
That is, the filter circuit 243A has a first coil and the filter circuit 243B has a second coil.
As will be described later, the first coil and the second coil are arranged side by side on the same substrate.

3 is an exploded perspective view of the motor unit 220. FIG.
The electric motor 230 is housed in a motor housing 250 , and an output shaft 231 of the electric motor 230 protrudes from the motor housing 250 .
A substrate accommodating portion 260 is provided integrally with the motor housing 250 on the base end side of the output shaft 231 .

The board accommodating portion 260 accommodates a board 270 on which various electronic components constituting the driving device 240 and circuit components such as the connectors 245A and 245B are mounted.
The connector 245A is a connector for supplying power to the first control unit 240A, and the connector 245B is a connector for supplying power to the second control unit 240B.

The board accommodating portion 260 is formed of a frame 251 attached to the end of the motor housing 250 and a cover 252 attached to the frame 251 so as to cover the open end of the frame 251 .
In other words, the space surrounded by the motor housing 250 , the frame 251 and the cover 252 is used as the substrate accommodation portion 260 , and the motor housing 250 , the frame 251 and the cover 252 form a housing that accommodates the substrate 270 .
The board 270 is housed in the board housing portion 260 so that its mounting surface is perpendicular to the axis of the output shaft 231 of the electric motor 230, and is fixed to the frame 251 using screws or the like.
In other words, the electric motor 230 is coupled to the housing that accommodates the board 270 .

A rotation detecting element 280 such as a Hall element for detecting the rotational position of the electric motor 230 is mounted on the substrate 270 together with the circuit components that constitute the driving device 240 .
A base end portion 231 a of an output shaft 231 of the electric motor 230 is provided so as to protrude from the motor housing 250 into the substrate housing portion 260 , and a magnet 281 is attached to the base end portion 231 a protruding into the substrate housing portion 260 . be.

A rotation detection element 280 (magnetic detection sensor) is mounted on the substrate 270 so as to face the magnet 281 .
Rotation detection element 280 detects the rotational position of electric motor 230 by detecting the magnetic flux of magnet 281 .
Note that the rotation detection element 280 can be a package sensor in which two rotation detection elements are integrated into one package.

FIG. 4 is a circuit diagram showing filter circuits 243A and 243B.
The filter circuit 243A is composed of a coil LA (first coil) and capacitors CA1 to CA4.
Coil LA is connected in series between the positive terminal of battery 290 and the load (inverter circuit 244A).
A power line between coil LA and the positive terminal of battery 290 is grounded through capacitor CA1.
Further, the power line between the coil LA and the load is grounded via capacitors CA2, CA3 and CA4, respectively.

The filter circuit 243B is composed of a coil LB (second coil) and capacitors CB1-CB4.
Coil LB is connected in series between the positive terminal of battery 290 and the load (inverter circuit 244B).
A power line between the coil LB and the positive terminal of the battery 290 is grounded via a capacitor CB1.
Further, the power line between the coil LB and the load is grounded via capacitors CB2, CB3 and CB4, respectively.

FIG. 5 is a top view showing one mode of arrangement of the coils LA and LB, the capacitors CA and CB, and the rotation detection element 280 that constitute the filter circuits 243A and 243B shown in FIG.
Note that the rotation detection element 280 and at least the filter circuits 243A and 243B of the components constituting the driving device 240 are arranged on the same substrate.
Substrate 270 can be composed of a plurality of substrates that are stacked on top of each other.
In this case, the parts other than the filter circuits 243A and 243B among the parts constituting the driving device 240 can be mounted on a board different from the board on which the filter circuits 243A and 243B are mounted.

The capacitor CA1, the coil LA, the capacitor CA2, the capacitor CA3, and the capacitor CA4 that constitute the filter circuit 243A are arranged linearly (in other words, in a line) on the substrate 270 in this order.
Also, the capacitor CB1, the coil LB, the capacitor CB2, the capacitor CB3, and the capacitor CB4 that constitute the filter circuit 243B are also linearly arranged on the substrate 270 in this order.

Here, the arrangement of the capacitors CA1 to CA4 and the coil LA forming the filter circuit 243A (in other words, the arrangement of the capacitors CA1 to CA4 and the coil LA) and the arrangement of the capacitors CB1 to CB4 and the coil LB forming the filter circuit 243B. (in other words, the capacitors CB1 to CB4 and the row of coils LB) are arranged in parallel.
Furthermore, the coil LA and the coil LB are arranged horizontally (in other words, in a horizontal line), and the capacitors CA1-CA4 and the capacitors CA1-CA4 are arranged horizontally.
In other words, the capacitors CA1 to CA4 and the coil LA forming the filter circuit 243A and the capacitors CB1 to CB4 and the coil LB forming the filter circuit 243B are arranged line-symmetrically.

Then, the rotation detection element 280 is arranged at the center of the area sandwiched between the coil LA and the coil LB, in other words, at the position on the substrate 270 which is equidistant from the coil LA and the coil LB and which is the shortest distance. There is.
In other words, the filter circuit 243A and the filter circuit 243A and the filter circuit 243A are arranged so that the rotation detection element 280 is arranged on the substrate 270 in accordance with the position of the output shaft 231 of the electric motor 230, and the rotation detection element 280 is sandwiched between the coil LA and the coil LB. The components of circuit 243B are linearly aligned.
That is, the capacitors CA1 to CA4 and the coil LA forming the filter circuit 243A and the capacitors CB1 to CB4 and the coil LB forming the filter circuit 243B are the rotation detection elements when viewed from the direction orthogonal to the mounting surface of the substrate 270. They are arranged symmetrically with respect to a straight line passing through 280 .

In this way, when the rotation detection element 280 is arranged in the region sandwiched between the coil LA and the coil LB, the output of the rotation detection element 280 is affected by the electromagnetic wave noise of the coil LA and the coil LB. There is a possibility that the detection accuracy of the rotational position will be lowered, and that the control accuracy of the electric motor 230 will be lowered.
Therefore, in order to prevent the electromagnetic wave noise of the coils LA and LB from affecting the output of the rotation detecting element 280, the coils LA and LB are configured to generate magnetic fields in opposite directions. .

FIG. 6 is a diagram for explaining how the coil LA and the coil LB generate magnetic fields in opposite directions.
Coil LA and coil LB are arranged such that the coil axial direction is perpendicular to the mounting surface of substrate 270 .
Further, the coil LA and the coil LB are configured so that current flows in the direction away from the mounting surface of the substrate 270 .
Further, the coil LA is wound to the right with respect to the current direction, and the coil LB is wound to the left with respect to the current direction.

That is, the coil axial direction of the coil LA and the coil axial direction of the coil LB are parallel to each other, and the current direction of the coil LA and the coil LB is the same, and the winding directions are opposite to each other. .
As a result, the coil LA and the coil LB generate magnetic fields in directions opposite to each other.

If the coil LA and the coil LB generate magnetic fields in opposite directions, the magnetic fluxes of the coil LA and the coil LB cancel each other out in the rotation detecting element 280 positioned at the same distance from the coil LA and the coil LB. , the electromagnetic interference (electromagnetic noise) received by the rotation detecting element 280 can be reduced as much as possible.
Therefore, it is possible to prevent deterioration in the detection accuracy of the rotational position of the electric motor 230 by the rotation detection element 280 due to the electromagnetic wave noise of the coils LA and LB.
In addition, since the capacitors CA2 to CA4 forming the filter circuit 243A and the capacitors CB2 to CB4 forming the filter circuit 243B are arranged symmetrically with respect to the rotation detecting element 280, the rotation detecting element 280 is also affected. noise can be reduced.

By the way, in the embodiments shown in FIGS. 2 and 4 to 6, two coils that generate magnetic fields in opposite directions are provided in the redundant filter circuits 243A and 243B of the control units 240A and 240B. However, the electric motor drive device according to the present invention is not limited to one having a redundant drive system.
For example, when the electric motor 230 has only one set of windings, and one filter circuit provided in the drive system for controlling the energization of the one set of windings has two coils connected in parallel, Two such coils connected in parallel can be configured to generate magnetic fields in opposite directions.

FIG. 7 is a circuit diagram showing one aspect of the filter circuit 243 including two coils connected in parallel.
In filter circuit 243, coil L1 (first coil) and coil L2 (second coil) are connected in parallel. is connected in series between
Furthermore, the power supply line between the parallel connection circuit of the coils L1 and L2 and the positive terminal of the battery 290 is grounded through the capacitor C1, and the parallel connection circuit of the coils L1 and L2 and the load (inverter circuit 244) are grounded. are grounded via capacitors C2, C3 and C4, respectively.

FIG. 8 is a top view showing one mode of arrangement of the coils L1 and L2, the capacitor C, and the rotation detection element 280 that constitute the filter circuit 243 shown in FIG.
Here, the coils L1 and L2 are configured to generate magnetic fields in directions opposite to each other, as shown in FIG.
Also, the coils L1 and L2 are arranged symmetrically with respect to a straight line passing through the rotation detecting element 280, but the rotation detecting element 280 is arranged closer to the inverter circuit 244 than the position sandwiched between the coils L1 and L2. .

In other words, while arranging the rotation detection element 280 avoiding the parallel connection circuit of the coils L1 and L2, the coils L1 and L2 are arranged symmetrically with respect to a straight line passing through the rotation detection element 280, and the coils L1 and L2 are arranged. A rotation detection element 280 is arranged on the substrate 270 at an equal distance from each of the coils L2.
Even in such a configuration, since the magnetic fluxes of the coils LA and LB cancel each other out in the rotation detecting element 280 positioned equidistant from each of the coils LA and LB, electromagnetic noise from the coils L1 and L2 is transmitted to the rotation detecting element 280. As a result, it is possible to prevent the detection accuracy of the rotational position of the electric motor 230 from being lowered.
As shown in FIG. 8, in addition to the capacitors C2 to C4 constituting the filter circuit 243, the capacitors C are arranged symmetrically around the rotation detecting element 280 with the rotation detecting element 280 as a boundary. , a capacitor C5 constituting another circuit can be arranged.

Each of the technical ideas described in the above embodiments can be used in appropriate combination as long as there is no contradiction.
Although the content of the present invention has been specifically described with reference to preferred embodiments, it is obvious that those skilled in the art can make various modifications based on the basic technical idea and teaching of the present invention. is.

Although the filter circuits shown in FIGS. 4 and 7 include a coil L and four capacitors C, the number of capacitors C constituting the filter circuit is not limited.
Moreover, the filter circuit is not limited to the filter circuit connected between the power relay and the inverter circuit.
Further, the filter circuit provided with the two coils connected in parallel, as shown in FIG. 7, can be used as drive circuits respectively provided in the first drive system and the second drive system.

Also, the arrangement shown in FIG. 5 can be changed as appropriate within a range in which the effects can be maintained.
For example, the position of the rotation detecting element 280 is fixed, the positions of all the parts constituting the filter circuit 243A are shifted upward in FIG. The position of the product can be shifted from the position shown in FIG. 5 toward the bottom in FIG. 5 by a predetermined distance α.

Even when such an arrangement is adopted, the rotation detection element 280 can be arranged at a position equidistant from the coil LA and the coil LB, and the coil LA and the coil LB generate magnetic fields in opposite directions. .
Therefore, it is possible to prevent the electromagnetic wave noise of the coil LA and the coil LB from acting on the rotation detecting element 280 and lowering the detection accuracy of the rotational position of the electric motor 230 .
In other words, the filter circuit 243A and the filter circuit 243B are not limited to being arranged line-symmetrically with respect to a straight line passing through the rotation detection element 280, and the example parts of the filter circuit 243A and the part array of the filter circuit 243B are They can be offset relative to each other in the column direction.

5, the rotation detecting element 280 is arranged at a position sandwiched between the coil LA and the coil LB. It can be arranged at a position avoiding the area sandwiched between the coil LA and the coil LB on the side.
Also in this case, the coil LA and the coil LB can be arranged symmetrically with respect to a straight line passing through the rotation detecting element 280, and the rotation detecting element 280 is arranged at a position equidistant from the coil LA and the coil LB. It will be.
Therefore, it is possible to prevent the electromagnetic wave noise of the coil LA and the coil LB from acting on the rotation detecting element 280 and lowering the detection accuracy of the rotational position of the electric motor 230 .

Further, in the aspect of the present invention shown in FIG. 6, the coil axial direction of the coil LA (first coil) and the coil LB (second coil) is the direction orthogonal to the mounting surface of the substrate 270, but the coil axial direction is parallel to the mounting surface of the substrate 270, and the coil LA (first coil) and the coil LB (second coil) generate magnetic fields in opposite directions.
Even when the coil axial direction is set in this way, the magnetic fluxes of the coil LA and the coil LB can be made to cancel each other, and the electromagnetic wave noise acts on the rotation detection element 280, causing the rotation position of the electric motor 230 to change. can be suppressed from lowering the detection accuracy of

DESCRIPTION OF SYMBOLS 100... Vehicle, 200... Electric power steering apparatus, 220... Motor unit, 230... Electric motor, 240... Drive device, 243A, 243B... Filter circuit, 270... Substrate, LA... Coil (first coil), LB... Coil ( second coil)

Claims (8)

An electric motor driving device for driving an electric motor,
A filter circuit comprising a first coil and a second coil arranged in parallel with the first coil,
the first coil and the second coil generate magnetic fields in opposite directions;
Electric motor drive. An electric motor driving device according to claim 1,
The first coil and the second coil are arranged such that the coil axial directions are parallel to each other,
Electric motor drive. The electric motor drive device according to claim 2,
A rotation detection element for detecting the rotational position of the electric motor is arranged equidistant from the first coil and the second coil,
Electric motor drive. An electric motor driving device according to claim 3,
The first coil and the second coil are arranged symmetrically with respect to a straight line passing through the rotation detecting element.
Electric motor drive. An electric motor drive device according to claim 4,
The rotation detection element is arranged at a position sandwiched between the first coil and the second coil,
Electric motor drive. An electric motor drive device according to claim 4,
The first coil and the second coil have the same current direction and opposite winding directions,
Electric motor drive. An electric motor driving device according to claim 1,
The electric motor has a first winding set and a second winding set,
The first coil is provided in a first filter circuit that constitutes a first drive system that controls energization of the first winding set,
The second coil is provided in a second filter circuit that constitutes a second drive system that controls energization of the second winding set,
Electric motor drive. An electric motor driving device according to claim 1,
The first coil and the second coil are connected in parallel,
Electric motor drive.

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